1. Field of the Invention
The present invention relates to an irrigation system with sprinkler heads which are capable of being drawn below ground surface when not in use.
2. Description of the Prior Art
In the past, the irrigation of agricultural fields, golf courses and lawns has either been carried out by fixed installations that are at least partially located at the ground surface of a field or movable systems that are supported on the ground. However, fixed installations interfere with the mowing, plowing and cultivating of the fields, fairways or lawns on which they are located. Movable irrigation systems, on the other hand present a nuisance in that they have to be broken down and set up at regular intervals.
In my U.S. Pat. No. 3,752,403 I disclosed a sprinkler system that is buried well below the ground surface so that the system does not interfere with mowing, plowing and cultivating operations. The system uses a plurality of cylinder and piston assemblies which are disposed vertically upright under the ground. Each sprinkler riser pipe in that system is secured to a piston and extends upwardly through a central opening in the upper end wall of a cylinder. A suitable sprinkler head that is capable of piercing through the ground is fixed to the upper end of the riser pipe.
Pressurized water directed into a lower port in the lower end of the cylinder urges the piston, the riser pipe, and the sprinkler head upwardly together, whereby the sprinkler head breaks up through the surface of the soil and is capable of watering a large area. The riser pipe and sprinkler head are retracted back beneath the surface of the soil by relieving water pressure from the lower cylinder part and supplying water pressure to the upper cylinder port to force the piston downwardly toward the bottom of the cylinder and draw the riser pipe and sprinkler head back well below ground level.
After using the system a few years I have discovered that although it works, it wastes water in that whenever the piston starts to move upwardly, water commences to flow immediately and continuously up through the riser pipe and out of the sprinkler head. The premature ejection of water while the riser pipe is moving upwardly causes excessive and wasteful watering in the immediate vicinity of the sprinkler head. Furthermore, the ejection of the water from the sprinkler head as it rises upwardly through the soil creates significant erosion in the area immediately above the cylinder.